1. Field
The following description relates to an antenna and a Radio Frequency Identification (RFID) tag.
2. Description of the Related Art
A radio frequency identification (RFID) tag is used in cooperation with a radio frequency identification (RFID) reader in various fields including materials management, security and so on. In general, if an object to which an RFID tag is attached is placed within a read zone of a RFID reader, the RFID reader modulates an RF signal having a predetermined carrier frequency and transmits an interrogation signal to the RFID tag. The RFID tag responses to the interrogation signal of the RFID reader.
That is, the RFID reader modulates continuous electromagnetic waves having a predetermined frequency to transmit an interrogation signal to the RFID tag. Then, the RFID tag performs a back-scattering modulation on the interrogation signal, thereby providing the RFID reader with information of the RFID tag stored in an internal memory thereof.
Back-scattering modulation is a transmission technology in which an RFID tag modulates the intensity or the phase of electromagnetic waves transmitted from an RFID reader through scattering, thereby sending information of the RFID tag to the RFID reader in the modulated electromagnetic waves.
A passive RFID tag rectifies electromagnetic waves transmitted from an RFID reader and uses the rectified electromagnetic waves as an operation power source thereof. In order for the passive RFID tag to normally operate, the intensity of signals received in the RFID tag needs to exceed a predetermined threshold value. In addition, to increase a read range of a passive RFID system, the RFID reader needs to maximize power transfer. However, since the power transfer of the RFID reader is subject to local regulations of the relevant country in addition to the federal communication commission (FCC) of the USA, the increase of power transfer is limited by the regulations. Accordingly, in order to maximize a read range of an RFID reader when the power transfer is limited, an RFID tag needs to effectively receive electromagnetic waves transmitted from the RFID reader.
As an example of enhancing the efficiency of an RFID tag, an additional matching circuit may be used. In general, an RFID tag includes an antenna, an RF front-end and a signal processor. The RF front-end and the signal processor are integrated into a signal chip. In this case, the antenna is conjugate-matched to the RF front end through the additional matching circuit, thereby maximizing the intensity of signals transmitted from the antenna to the RF front end. However, such a matching circuit including a capacitor and an inductor takes up a large area on a chip, resulting in disadvantages with respect to miniaturization and cost.